Classifications

• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
  • D04H1/542—Adhesive fibres
  • D04H1/544—Olefin series
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/04—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins
  • D01F6/06—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins from polypropylene
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/30—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising olefins as the major constituent
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
  • D01F6/46—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds of polyolefins
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
  • D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
  • D04H3/16—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion

Definitions

• the present invention relates to polyolefin fibers suitable for the production of nonwoven fabrics by spun-bonding process, having improved strength and softness characteristics.
• the present invention also relates to a process for the production of said fibers, a process to produce nonwoven fabrics by spun-bonding using said fibers, and the nonwoven fabrics obtained by said process.
• fibers includes also products similar to fibers, such as fibrils.
• Nonwoven fabrics are widely used in various applications. They are used, for example, in the preparation of articles to be utilized in the agricultural field, and for domestic and industrial "throwaway" articles. For some specific uses said fabrics must possess good softness characteristics (which depend on the flexibility index of the fiber), strength (which depends on the thermowelding strength of the fiber) and resistance to yellowing. These characteristics are particularly important in the health and medical fields.
• Polyolefin fibers which can be used for the preparation of nonwoven fibers possessing good aging and yellowing resistance are already known in the art.
• fibers with the above mentioned properties are described in published European patent application EP-A-391438, in the name of the Applicant.
• Said patent application describes some combinations of stabilizers which can render the fibers particularly resistant to yellowing and aging.
• Published European patent application EP-A-598 224 in the name of the Applicant describes nonwoven fabrics which have, among other things, good softness and strength properties (in the examples the maximum thermowelding strength of the fibers constituting the fabrics is slightly higher than 3 N).
• One embodiment of the present invention is a process for the preparation of nonwoven fabrics which comprise said fibers and present both softness and strength properties.
• Another embodiment of the present invention is a process used to prepare said fibers.
• Yet another embodiment of the present invention relates to the nonwoven fabrics obtained with said process.
• the present invention provides a fiber for nonwoven fabrics having thermowelding strength equal to or greater than 5 N and/or flexibility higher than 800, comprising a polymer material additivated with organic phosphites and/or phosphonites, HALS and optionally phenolic antioxidants, said polymer material being selected from:
• the C4-C8 ⁇ -olefins to be used for the preparation of the copolymers which can be present in random copolymers (2), Fraction A and Fraction C are linear or branched alkenes, and are preferably selected from the following compounds: 1-butene, 1-pentene, 1-hexene, 1-octene and 4-methyl-1-pentene.
• the 1-butene is the preferred ⁇ -olefin.
• the random copolymers (2) contain a quantity of comonomer ranging from 0.05 to 20% by weight. When the quantity of comonomer exceeds 5%, said copolymers must be blended with the propylene homopolymer.
• Fraction A is present in the heterophasic polymer in quantities ranging from 10 to 50 parts by weight, and is made up of a propylene homopolymer with an isotactic index preferably greater than 90, more preferably from 95 to 98, or of the copolymer defined above, preferably containing over 85%, more preferably from 90 to 99% of propylene.
• Fraction B is present in the heterophasic polymer in quantities ranging from 7 to 15 parts by weight and has a crystallinity ranging from about 20 to 60%, determined by way of DSC (Differential Scanning Calorimetry).
• the copolymer of said fraction is preferably selected from the following types of copolymers: ethylene/propylene, containing over 55% of ethylene; ethylene/propylene/C4-C8 ⁇ -olefin, containing from 1 to 10% of said ⁇ -olefin and from 55% to 98%, preferably from 80 to 95%, of ethylene plus said ⁇ -olefin; ethylene/C4-C8 ⁇ -olefin, containing from 55% to 98%, preferably from 80 to 95%, of said ⁇ -olefin.
• Fraction C is present in the heterophasic polymer in quantities ranging from 30 to 75 parts by weight, and is made up of a copolymer selected from: an ethylene/propylene copolymer containing from 15% to 70% of ethylene, preferably from 20 to 60%; an ethylene/propylene/C4-C8 ⁇ -olefin copolymer, containing from 1 to 10% of said ⁇ -olefin, preferably from 1 to 5%, wherein the total quantity of ethylene plus ⁇ -olefin ranges from 20 to less than 40%; an ethylene/ ⁇ -olefin copolymer, containing from 20 to less than 40%, preferably from 20 to 38%, more preferably from 25 to 38%, of said ⁇ -olefin.
• a copolymer selected from: an ethylene/propylene copolymer containing from 15% to 70% of ethylene, preferably from 20 to 60%; an ethylene/propylene/C4-C8 ⁇ -olefin copoly
• the dienes, optionally present in the copolymers of said Fraction are present in quantities equal to or less than 10%, and are preferably selected from: butadiene, 1,4-hexadiene, 1,5-hexadiene and 2-ethylidene-5-norbornene.
• the heterophasic propylene polymers are prepared either by mechanically blending components (A), (B), and (C) in the molten state, or by using a sequential polymerization process carried out in one or more steps, and using highly stereospecific Ziegler-Natta catalysts.
• heterophasic polypropylene compositions mentioned above as well as the catalysts and polymerization processes commonly used for their preparation, are described in published European patent applications 400333 and 472946.
• the blends (3) are obtained by melting and pelletizing the polymers, or by blending them without melting.
• the quantity of heterophasic polymer and/or random copolymer (2) containing over 5% of comonomer preferably does not exceed 30% of the total weight of the blend.
• the stabilizers which are added to the polyolefins described above are the following:
• phosphites that can be used as additives for the polyolefins of the fibers of the present invention: tris(2,4-di-tert-butylphenyl)phosphite, marketed by CIBA GEIGY under the trademark Irgafos 168; distearyl pentaerythritol diphosphite, marketed by BORG-WARNER CHEMICAL under the trademark Weston 618; 4,4'-butylidenebis(3-methyl-6-tert-butylphenyl-di-tridecyl)phosphite, marketed by ADEKA ARGUS CHEMICAL under the trademark Mark P; tris(monononyl phenyl)phosphite; bis(2,4-di-tert-butyl)pentaerythritol diphosphite, marketed by BORG-WARNER CHEMICAL under the trademark Ultranox 626.
• the preferred organic phosphonite that can be used as additive for the polyolefins of the fibers of the present invention is tetrakis(2,4-di-tert-butylphenyl)4,4-diphenylene diphosphonite, marketed by SANDOZ under the trademark Sandostab P-EPQ.
• HALS that can be added to the polyolefins of the fibers of the present invention are: poly ⁇ [6-(1,1,3,3,-tetramethylbutyl)-imine]-1,3,5-triazine-2,4-diol] [2-(tetramethylpiperidyl)amine]hexamethylene-[4-(2,2,6,6-tetramethylpiperidyl)imine ⁇ (Chimassorb 944), Chimassorb 905, bis(2,2,6,6,-tetramethyl-4-piperidyl)sebacate (Tinuvin 770), Tinuvin 992, poly(N- ⁇ -hydroxymethyl-2,2,6,6,-tetramethyl-4-hydroxy-piperidyl succinate (Tinuvin 622), Tinuvin 144, Spinuvex A36, marketed by CIBA-GEIGY; Cyasorb UV 3346 marketed by AMERICAN CYANAMIDE.
• phenolic antioxidants to be used as additives in the polyolefins making up the fibers of the present invention are: tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-s-triazine-2-4-6-(1H,3H,5H)-trione, sold by AMERICAN CYANAMID under the Cyanox 1790 trademark; calcium bi[monoethyl(3,5-di-tert-butyl-4-hydroxybenzyl)phosphonate]; 1,3,5-tris (3,5-di-tertbutyl-4-hydroxybenzyl)-s-triazine-2,4,6(1H,3H,5H)trione; 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl)benzene; pentaerythrityltetrakis[3-(3,5-di-tert-butyl-4-hydroxy-phen
• the usual additives such as pigments, opacifiers, fillers, UV stabilizers, and flame retardants.
• the polymers (containing the necessary additives) which are converted in fibers according to the present invention have a melt flow rate (MFR) ranging from 5 to 40 g/10 min.
• MFR melt flow rate
• the polymers of points (1) and (2) have a MFR preferably ranging from 5 to 25 g/10 min.
• the MFR is measured according to ASTM D 1238, condition L. High MFR values are obtained directly in polymerization, or by controlled radical visbreaking.
• controlled radical visbreaking is carried out using, for example, some organic peroxides, such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, during the pelletizing phase or directly in the fiber extrusion step.
• organic peroxides such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane
• the molecular weight distribution of the polymers making up the fibers of the present invention ranges from 3 to 6, preferably from 3.5 to 4.5.
• the polymers to be converted into the fibers of the present invention can be in the form of pellets or nonextruded particles, such as flakes, or spheroidal particles with a diameter ranging from 0.5 to 4.5 mm. Said particles are covered or impregnated, at least on the surface, with the stabilizers (or additives in general) mentioned above, and/or peroxides, if the latter should be necessary to obtain a molecular weight distribution within the range mentioned above.
• Additives such as opacifiers, fillers and pigments can also be added while the fiber is being spun.
• the spinning process must be carried out preferably at a die temperature ranging from 240°C to 320°C, and a hole flow-rate from 0.25 to 0.4 g/min/hole for polymers (1) and (2) having MFR ranging from 5 to 25 g/10 min., or it can be carried out preferably at a die temperature ranging from 230°C to 300°C and a hole flow-rate from 0.25 to 0.4 g/min/hole for polymer blends (3) having a MFR ranging from 5 to 40 g/10 min.
• the fibers thus obtained have a flexibility index higher than 800 and a thermowelding strength not lower than 5 N.
• the process for the production of the fibers is also an embodiment of the present invention.
• the process for the preparation of fibers according to the present invention is carried out by using extruders equipped with a die and without subjecting the fibers to a subsequent drawing.
• the die is characterized by a real or equivalent output hole diameter of less than 0.5 mm, preferably ranging from 0.2 to 0.48 mm.
• output diameter of the holes is meant the diameter of the holes measured at the external surface of the die, i.e. on the front face of the die from which the fibers exit. Inside the thickness of the die, the diameter of the holes can be different from the one at the output.
• the "equivalent output diameter" definition applies to those cases where the hole shape is not circular.
• the temperature of both the extruder and the die during the processing of the polymers ranges from 230°C to 320°C; in particular it is best to operate at temperatures ranging from 240°C to 320°C when the fibers are obtained from polymers (1) and (2), while when using the polymer blends (3) the temperatures can range from 230°C to 300°C.
• the dimensions of the fibers of the present invention if they are to be used for the preparation of nonwoven fabrics, have a count ranging from 1 to 10 dtex.
• the hole flow-rate must range from 0.1 to 0.6 g/min/hole, preferably from 0.25 to 0.45 g/min/hole.
• MFR Melt Flow Rate
• ASTM-D 1238 condition L.
• GPC Gel Permeation Chromatography
• GPC Gal Permeation Chromatography
• Thermowelding strength in order to evaluate the thermoweldability of staple fibers, one manufactures a nonwoven fabric with the fiber being tested by way of calendering under set conditions. Then one measures the strength needed to tear said nonwoven fabric when the stress is applied in directions which are both parallel and transversal to that of the calendering.
• thermoweldability index (TM ⁇ TC) 1/2
• TM and TC represent the tear strengths of the nonwoven fabric measured according to ASTM 1682, for the parallel and transversal directions respectively, and expressed in Newton.
• the value of the strength determined in this fashion is considered a measure of the capability of the fibers to be thermowelded.
• the result obtained is influenced substantially by the characteristics regarding the finishing of the fibers (crimping, surface finishing, thermosetting, etc.), and the conditions under which the card web fed to the calender is prepared. To avoid these inconveniences and obtain a more direct evaluation of the thermoweldability characteristics of the fibers, a method has been perfected which will be described below in details.
• thermoweldability of film After the roving was twisted eighty times, the two extremities were united, thus obtaining a product where the two halves of the roving are entwined as in a rope. On said specimen one produced one or more thermowelded areas by means of a thermowelding machine commonly used in a laboratory to test the thermoweldability of film.
• a dynamometer was used to measure the average strength required to separate the two halves of the roving at each thermowelded area. The result, expressed in Newton, was obtained by averaging out at least eight measurements.
• the welding machine used was the Brugger HSC-ETK.
• the clamping force of the welding plates is 800 N; the clamping time was 1 second, and the temperature of the plates was 150°C.
• the specimen has the same characteristics as the one used to measure thermowelding strength and is prepared using the same process described above.
• Norm ISO/TC 38/SC1 at 60°C was applied to measure the resistance of the fibers to fading caused by gases produced by hydrocarbon combustion.
• the resistance to yellowing value referred to in the examples concerns the variation caused by gas fading measured at 60°C after 4 cycles.
• Flake polypropylene having a MFR of 2 g/10 min. and additivated with the same additives listed in Example 1, is visbroken with Lupersol until it reaches a MFR of 12 g/10 min, and a Mw/Mn of 4. 10 kg of said polymer are then subjected to spinning in the spinning apparatus described in Example 1.
• a polymer blend comprising: 90 parts by weight of polypropylene having a MFR of 5 g/10 min., and 10 parts by weight of heterophasic polymer having a MFR of 5 g/10 min, intrinsic viscosity of 2.6 dl/g, and the following composition: 55% by weight of ethylene/propylene random copolymer (containing 2.5% of ethylene), and 45% by weight of ethylene/propylene rubber at a 60/40 ratio is used.
• the polymer blend additivated with the same additives of Example 1 and visbroken with Lupersol 101 until a MFR of 35 g/10 min. is reached, is subjected to spinning, under the conditions listed in Table 1, in the spinning apparatus described in Example 1.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Artificial Filaments (AREA)
• Nonwoven Fabrics (AREA)

Applications Claiming Priority (2)

Publications (3)

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Family Applications (1)

Country Status (7)

Cited By (11)

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Citations (4)

• 1993
  • 1993-06-17 IT IT93MI001309A patent/IT1264840B1/it active IP Right Grant
• 1994
  • 1994-06-16 FI FI942890A patent/FI942890A/fi unknown
  • 1994-06-16 CA CA002126014A patent/CA2126014A1/fr not_active Abandoned
  • 1994-06-16 KR KR1019940013637A patent/KR100304296B1/ko not_active IP Right Cessation
  • 1994-06-17 DE DE69430026T patent/DE69430026T2/de not_active Expired - Fee Related
  • 1994-06-17 EP EP94109404A patent/EP0632147B1/fr not_active Expired - Lifetime
  • 1994-06-17 JP JP6159157A patent/JPH07166416A/ja active Pending

Patent Citations (4)

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